A semiconductor acceleration sensor manufactured using a process of manufacturing a semiconductor device has been conventionally used. An example of this semiconductor acceleration sensor is disclosed, for example, in Japanese Patent Laying-Open No. 2008-139282 (PTD 1). In this acceleration sensor, a detection frame is supported by a substrate via a torsion beam so as to be rotatable. An inertia mass body is supported by the detection frame via a link beam so as to be displaceable in a thickness direction of the substrate. A detection electrode is formed on the substrate so as to face the detection frame.
In this acceleration sensor, when acceleration is applied in a direction perpendicular to the substrate, the inertia mass body is displaced in the direction perpendicular to the substrate. This displacement of the inertia mass body is transferred to the detection frame via the link beam, causing the detection frame to rotate around the torsion beam. This rotation leads to a change in distance between the detection frame and the detection electrode, which leads to a change in capacitance between the detection frame and the detection electrode. The acceleration is measured from this change in capacitance.
In a method of manufacturing this acceleration sensor, after the detection electrode is formed on the substrate, a sacrificial film is deposited on the entire substrate. After the detection frame (movable structural body) is formed on this sacrificial film, this sacrificial film is removed, so that the detection frame (movable structural body) is rendered displaceable. Then, a cap is supported on the substrate so as to cover the detection frame (movable structural body).